The invention relates to a method and an apparatus for measuring the torque transmitted through a rotating machine element, by means of two parts connected to this machine element with axial and/or radial spacing, which rotate relative to one another. When torque is transmitted through the machine element, the relative rotation occurring in the circumferential direction between these two parts is utilized for determining the torque transmitted.
In a known measuring method of this kind, two gear wheels functioning as pulse transducers are mounted, spaced axially apart, on the machine element, for example a shaft. Their spacing is selected such that when torque is transmitted a measurable relative rotation takes place between the two wheels, because of the elasticity of the shaft. As a result, there is a temporal displacement between the pulse trains generated by the two wheels. From this displacement, the transmitted torque can be calculated.
However, with this method torque can be measured only with a rotating machine element, while contrarily it is often desirable in practice to measure the torque acting upon machine elements while they are at a standstill, for instance for starting the machine only once the measured torque is within the prescribed limits.
A further disadvantage of this known measuring system is that a structure of great axial length is required, because the two pulse transducers must be disposed far from one another in order to produce an angular difference between them that is sufficient for measuring purposes.
Another measuring principle is used with torque-measuring hubs. Here, however, the machine element that is to be tested has to be interrupted so that the measuring hub can be built into it. Also, a new bearing for the interrupted machine element must be provided on both sides of the measuring hub. Hence a great deal of installation space is still required. The apparatus cannot be retroactively installed in existing systems.